Recently, in the ink-jet printing industry, which has been significantly growing, the realization of high-performance ink-jet printers, the improvement of inks, etc. have markedly progressed, and it has become possible to obtain very fine and sharp images which have excellent printing properties and which are substantially equivalent to silver halide prints even in ordinary households. Therefore, ink-jet printers are not only used in homes but have also started to be used in various fields such as in the production of large advertisement boards.
The improvement in the image quality of ink-jet printed matter is mainly achieved by not only the improvement in the performance of printers but also the improvement in printing inks. Specific examples of the improvement in printing inks include studies on the selection of solvents in inks and the selection of dyes or pigments in inks. Recently, pigment inks, which are known as inks having good color-developing properties that are substantially equivalent to those of dye inks, have attracted attention.
However, even in the case where such a pigment ink having a good color-developing property is used, it may be difficult to form a printed image having a high color density and excellent printing properties because bleeding of the ink or the like may occur depending on the composition of an ink-receiving layer. Furthermore, with an increase in the type of ink-jet printed matter, various materials have been used as a support on which the ink-receiving layer is provided. Under this circumstance, an existing ink-receiving layer may be separated from a support with time because, for example, the ink-receiving layer does not have sufficient adhesion to a plastic film such as a polyethylene terephthalate film.
In addition, the use of known printing methods such as the ink-jet printing method and a screen printing method has been studied for the purpose of forming a conductive pattern of an electronic circuit or the like. This is because, with the recent requirements for improving the performance, reducing the size, and reducing the thickness of electronic devices, an increase in integration density and a reduction in thickness have also been strongly required for electronic circuits and integrated circuits that are used in the electronic devices.
A specific method for producing such a conductive pattern of an electronic circuit or the like includes printing a conductive ink containing a conductive substance such as silver on a surface of a support by an ink-jet printing method, a screen printing method, or the like, then drying the conductive ink, and performing heating or light irradiation, as required.
However, even when the conductive ink is printed directly on a surface of a support, the conductive ink does not readily adhere to the surface of the support and is easily separated from the support, which may result in, for example, a disconnection in an electronic circuit that is finally obtained. In particular, a support composed of a polyimide resin, a polyethylene terephthalate resin, or the like has flexibility and thus enables the production of flexible devices that can be bent. However, in particular, an ink, a resin, or the like does not readily adhere to such a support composed of a polyimide resin or the like and is easily separated from the support, which may result in a disconnection in an electronic circuit that is finally obtained and severing of electrical connection.
A known method for solving the above problem is a method for forming a conductive pattern by drawing a pattern, on an ink-receiving substrate having a latex layer thereon, using a conductive ink by a predetermined method. It is known that an acrylic resin can be used as the latex layer (refer to PTL 1).
However, an ink-receiving layer formed of the latex layer on which the conductive pattern is formed may cause bleeding of a conductive ink, unevenness of the printing thickness, etc. Accordingly, it may be difficult to form a conducting line formed of a fine line having a width of about 0.01 to 200 μm, which is generally required for realizing an increase in integration density of electronic circuits or the like.
In the formation of the conductive pattern, printed matter obtained by performing printing using a conductive ink is usually baked by heating at a temperature of about 80° C. or higher in order to provide the electrical conduction property by bringing conductive substances contained in the conductive ink into contact with each other.
However, an ink-receiving layer such as the latex layer described in PTL 1 is, for example, readily degraded by the effect of heat received in the baking step. Thus, in particular, the adhesion at the interface between the ink-receiving layer and the support tends to decrease, and separation tends to occur even when a very small force is applied.
In addition, during the baking step, the latex layer serving as the ink-receiving layer tends to be excessively swollen and deformed. Consequently, a disconnection in an electric circuit or the like and the failure of an electrical connection may occur. In addition, since the latex layer usually does not have sufficient adhesion to the support before the heating in the baking step is performed, the support may be partially separated from the ink-receiving layer before the baking step.
In the formation of the conductive pattern, a plating process is often performed on the surface of the conductive pattern using copper or another metal from the standpoint of forming a highly reliable wiring pattern that can maintain a good electrical, conduction property without the occurrence of a disconnection or the like for a long time.
However, chemical agents for plating, the chemical agents used in the plating process, and chemical agents used in a washing step of the plating process are usually strongly alkaline or acidic, and thus these chemical agents readily cause, for example, separation of the receiving layer etc. from the support. As a result, for example, a disconnection in the conductive pattern may be caused.
Accordingly, it is desired for the conductive pattern to have durability of such a level that the conductive-ink-receiving layer does not become separated from the support even when the conductive pattern is repeatedly immersed in the chemical agents and the like for a long time.